Lead exposure may be linked to 250,000 heart-disease deaths each year, study says

Water typically leaves a treatment plant lead free. It's on its way to your home that lead gets into your water.

Sean Heisey

Medical researchers have long known that lead-poisoning damages children’s brains and increases the risks of all sorts of health problems from high blood pressure to heart disease. Now new research has found that the deaths of an estimated 250,000 Americans from cardiovascular disease each year may be linked to lead exposure — a number far higher than previous estimates.

The study was based on a national health survey that tracked more than 14,000 participants across the country over nearly two decades.

Nicole Estes performs a water quality analysis in a laboratory at the Louisville Water Company's ...more

Nicole Estes performs a water quality analysis in a laboratory at the Louisville Water Company's Crescent Hill filter plant in Louisville, Kentucky, in 2016.

Luke Sharrett, for USA TODAY

In previous studies, researchers had assumed that low levels of lead in people’s blood wouldn’t increase the risk of death. But the new study found that even minute levels of lead substantially increase the risk of death, especially from heart disease.

“We saw risk down to the lowest measurable levels,” said Bruce Lanphear, a lead-poisoning researcher at Simon Fraser University in British Columbia who led the study. “It’s a big deal and it’s largely been ignored when it comes to cardiovascular disease deaths.”

Lead levels in the air have declined dramatically in the United States since the country began phasing out leaded gasoline in the 1970s. But lead water pipes are still being used in communities scattered across the country, and lead paint remains in many old houses.

Workers at construction sites and auto shops may be exposed to lead. It’s released into the air by coal-fired power plants, lead smelters and other industrial facilities, including recyclers that work with lead batteries. Lead can be found in products like fishing weights, lead-glazed ceramics and some children’s toys. It also continues to turn up in some foods, including baby foods.

The new study, which was published Monday in The Lancet Public Health journal, is the first to estimate the number of deaths in the U.S. linked to low-level lead exposure using data from a nationally representative sample.

Cardiovascular disease is the leading cause of death for Americans, and the study’s findings indicate that lead is a major factor contributing to those deaths.

The research focused on 14,289 people who were followed in the national health survey between 1988 and 1994, and again in 2011. Their health data included a blood test for lead.

At the end of the period, 4,422 people had died, including 1,801 from cardiovascular disease, out of which 988 deaths were from coronary heart disease. The researchers adjusted the results for a list of factors such as age, sex, alcohol consumption, smoking and diet, and estimated the proportion of deaths in U.S. adults ages 44 or older whose premature deaths could have been prevented if they hadn’t been exposed to lead.

They estimated that 256,000 deaths — nearly 29 percent of premature deaths from cardiovascular disease — could be linked to lead exposure each year. That included 185,000 deaths from coronary heart disease, or about 37 percent of all deaths from that cause, as well as other types of cardiovascular disease, such as strokes and peripheral artery disease.

Previous studies had assumed that there was no harm when patients had lead at concentrations of less than 50 parts per billion in their blood. About four out of five people in the survey had lead concentrations in their blood below that level, yet their cases still showed increasing risks with incremental rises in lead levels.

Lanphear said the results point to a need for the federal Environmental Protection Agency, as well as other federal and state agencies, to ratchet down the allowable levels of lead under their standards.

“The levels of lead in standards right now are too high to protect kids,” Lanphear said. “And this new study would suggest that they’re too high — whether it’s lead in water, lead in house dust, lead in air — all of those things should be reevaluated based upon this study because it suggests that there’s no safe level of lead.”

Water flows during a water quality test at a filter plant in Louisville, Kentucky, in 2016.

Water flows during a water quality test at a filter plant in Louisville, Kentucky, in 2016.

Luke Sharrett, for USA TODAY

Lanphear and his colleagues also looked at deaths from all causes and estimated that about 400,000 deaths per year are attributable to lead exposure in the United States. That’s 10 times larger than the current estimate and about 18 percent of all deaths. It’s also comparable to the approximately 480,000 current smokers who die in a given year.

Those numbers are based on the amounts of lead that older Americans were exposed to decades ago. Lanphear pointed out that most Americans are exposed to less lead nowadays because of lead has been taken out of gasoline and paint.

“So the number of deaths from lead exposure will be lower in younger generations,” he said. “Still, lead represents a leading cause of disease and death, and it is important to continue our efforts to reduce environmental lead exposure.”

Mariah Roseberry holds her son, Hudson, 17 months, as she answers questions about lead-poisoning risk factors in her home in Cincinnati on Jan. 5, 2018. Hudson tested at a blood lead level of 5.4. Medical professionals typically consider anything higher than 5.0 to be lead poisoning.

Sam Greene/The Enquirer

Low levels of lead in children's blood have been linked to lower IQs, slowed growth and behavioral and learning problems.

The recent crisis of lead-contaminated drinking water in Flint, Mich., focused more attention on the long-neglected problem of lead pipes in water systems across the country. In 2016, an investigation by the USA TODAY Network found nearly 2,000 water systems in all 50 states where testing showed excessive levels of lead contamination during the previous four years.

Reducing the amounts of lead that people are exposed to, Lanphear said, will require a variety of measures, including changing health standards, abating lead paint in older homes and phasing out leaded aviation fuel that’s still used for some small planes.

“Single-piston jet engines for these little planes at regional airports continue to use leaded gasoline,” Lanphear said, “and you can see measurable increases in the children who live closest to those regional airports.”

Philip Landrigan, dean for global health and a professor at the Icahn School of Medicine at Mount Sinai in New York, said one big takeaway is that lead has a much greater effect on deaths from cardiovascular disease than previously recognized.

“It sort of opens up a new window on heart disease,” said Landrigan, who wasn’t involved in the study.

The research adds lead to a list of long-recognized risk factors for heart disease including smoking, high blood pressure and obesity, and Landrigan said cardiologists and other doctors will probably start making blood-lead testing a standard part of their procedures in the next few years.

Beyond that, he said, the findings underscore the importance of doing away with remaining lead pipes and lead paint across the country.

“I think we have to really mobilize the resources in this country to get rid of that lead. We know how to do it, but we haven’t had the political leadership or the willingness to spend the money,” Landrigan said. “Anything that we could do that could knock heart disease down by 10 or 15 percent is saving a lot of lives.”

In a commentary article that accompanied the study, Landrigan wrote that deaths from cardiovascular disease increased 12.5 percent worldwide from 2005 to 2015, and that the biggest increases occurred in rapidly developing “low-income and middle-income countries,” which are industrializing and coping with pollution. Until now, he said, little attention has focused on the possible contribution of lead, or the contribution of all types of pollution.

Countries worldwide have phased out leaded gasoline. But lead production continues to grow, driven in part by rising global demand for car batteries.

While the study focused only on the United States, Lanphear said the finding have important implications for places where high levels of lead are much more prevalent, such as India and countries in Southeast Asia.

Howard Hu, a professor of environmental public health at the University of Toronto who wasn’t involved in the study, said the findings were impressive and in line with previous studies.

“I’m sure there’ll be a lot of critical interpretation and skepticism,” Hu said. He said he expects critics may question whether it’s really the level of lead that’s driving the trends, or “is it a proxy for some other unmeasured thing?”

“People will be scratching their heads trying hard to think of what else it could be a proxy for. I think they can think hard, but it’s hard to explain it away,” said Hu, who has also studied how lead affects chronic diseases. “It would be really hard to explain this away as really just an effect representing something else.”

Lanphear’s team included researchers from the University of California, Berkeley, the University of Rochester School of Medicine and Dentistry, and the University of Cincinnati School of Medicine.

They used standard, accepted methods to account for other factors like tobacco use, Hu said. “There are some things that one could argue could be measured better, like socioeconomic status, and they acknowledged that there might still be some undetected influence of socioeconomic status.”

Among other limitations, the study’s authors said they were unable to control for factors such as people’s exposure to arsenic or air pollution, which also pose health risks.

In this 2016 photo, signs warn people not to drink the lead-contaminated water from a water ...more

In this 2016 photo, signs warn people not to drink the lead-contaminated water from a water fountain at Woodside Church in Flint, Mich.

Jacquelyn Martin, AP

While Americans nationwide were exposed to more lead decades ago and have seen improvements, Hu pointed out that there are still pockets of people who are exposed to high levels.

“And it unfortunately now tracks even more towards poverty — living in old housing where there’s lead paint or lead plumbing or living close to factories that are still emitting lead.” Hu said. “We’ve done a pretty good job of reducing exposures over time, but there’s still lots more to do, as illustrated by the Flint water crisis.”

While it’s troubling that lead has long been overlooked as a major risk factor, Lanphear said, there’s also a hopeful side to the research.

“To the extent that we can identify risk factors, like lead or air pollution, and we can actually modify them, it’s really hopeful because it means that we know what to do to dramatically reduce deaths from heart disease,” he said.

And if the country takes the issue seriously in the coming years, he said, far fewer people could end up dying from heart disease.